This invention relates to a communication device. More particularly, a technology disclosed herein relates to a method of notifying a defect along a point-to-multipoint logical path in multiprotocol label switching (MPLS) and other transfer protocols where a connection-oriented logical path is built, to a logical path switching method, and to a communication device that has a logical path defect notifying function and a logical path switching function.
With the progress of IT and the broadening of the bandwidth of wide area networks (WANs) or metropolitan area networks (MANs), multimedia contents that are characterized by data distribution through streaming are increasing mainly among corporations as observed in, for example, a high-definition system for video conferencing involving multiple sites and live in-house broadcasting. Such streaming data are characterized by being distributed one-way through point-to-multipoint communication (i.e., from a start node which distributes the data to multiple end nodes which receive the data), and by their need for a regular, stable transmission path bandwidth for the distribution. Since those applications require real-timeness, communication breakdown due to a defect along the transmission path can lead to a huge loss in a user's benefit and is unacceptable. Network providers that provide the WAN/MAN service therefore need to provide a measure of detecting a defect in a point-to-multipoint path, and path protection.
Conventional technologies for protecting a connection-oriented point-to-multipoint path are described in JP 2000-36818 A and JP 2007-282153 A.
JP 2000-36818 A makes a suggestion about recovery from a defect in a point-to-multipoint path in a tree topology network. Specifically, the publication proposes recovery from a defect, in which a route that bypasses a detected defect between relay nodes is calculated based on adjacent node information that the devices hold, and the defect bypassing path is set.
JP 2007-282153 A makes a suggestion about recovery of a point-to-multipoint path in a ring topology network. Specifically, the proposed recovery from a defect utilizes the ring feature of the network topology to build a logical path such that end nodes of a point-to-multipoint path include the start node of the point-to-multipoint path. A normal communication point-to-multipoint path and an auxiliary communication point-to-multipoint path are also prepared. In the event of a defect, a node that has detected the defect notifies each end node of defect information via the point-to-multipoint path used for communication. Since the end nodes include the start node of the point-to-multipoint path, the defect information reaches the start node as well. Detecting the defect information, the start node switches from the normal communication point-to-multipoint path to the auxiliary communication point-to-multipoint path, and thus accomplishes a recovery from the defect.